Chemical analysis of liquids, such as water, milk and biological fluids is often desirable or necessary for health maintenance and diagnostic care. Various compositions and elements to facilitate such analyses are known. Such compositions and elements generally include a reagent composition for determining a chemical or biological substance under analysis, identified as an analyte herein. The reagent composition, upon interaction with the analyte, provides a detectable change (e.g. dye formation).
Recently, much work has been directed to developing compositions and elements which are useful for rapid and highly quantitative diagnostic or clinical analysis of biological fluids such as whole blood, serum, plasma, urine and the like.
For example, for the rapid and effective diagnosis and treatment of infectious diseases, it is desirable to be able to detect the bacteria causing the disease as rapidly as possible. Infections of the urinary tract are among the most common bacterial diseases, second in frequency only to infections of the respiratory tract. In fact, in many hospitals, urinary tract infections are the most common form of nosocomial infections, often following the use of in-dwelling catheters and various surgical procedures. Most urinary tract infections (UTI) result from ascending infection by microorganisms introduced through the urethra and vary in severity from an unsuspected infection to a condition of severe systemic disease. Such infections are usually associated with bacterial counts of 100,000 (10.sup.5) or more organisms per ml of urine, a condition referred to as significant bacteriuria. Under normal conditions, urine is sterile, although contamination from the external genitalia may contribute up to 1,000 (10.sup.3) organisms per ml in properly collected and transported specimens.
Further, in order to insure that a prescribed antibiotic is in fact effective in treating an infection, repeated tests during therapy are required. The need for simple, rapid bacteriuria testing is thus clear. Moreover, in view of the frequent unsuspected asymptomatic occurrences of UTI among children, pregnant women, diabetics and geriatric populations, diagnosis of which may require collection and testing of several specimens, bacteriuria tests must be sufficiently simple and economical to permit routine performance. Again, this illustrates the need for rapid and inexpensive bacteriuria detection methods.
A significant advance in the art for determination of various analytes, including microorganisms is described in copending and commonly assigned U.S. Ser. No. 824,766, filed Jan. 31, 1986 by Belly et al and entitled REDUCIBLE COMPOUNDS AND ANALYTICAL COMPOSITIONS, ELEMENTS AND METHODS UTILIZING SAME. The reducible compounds therein can be readily reduced in the presence of a reductant to release a detectable species, e.g. a dye, within a matter of minutes. Further, copending and commonly assigned U.S. Ser. No. 824,756, filed Jan. 31, 1986 by Babb et al and entitled BIOLOGICAL AND ANALYTICAL USES OF PHENALENONE AND BENZPHENALENONE COMPOUNDS relates to similar reducible compounds which rapidly release fluorescent phenalenone and benzphenalenone compounds in the presence of reductants. It has been observed, however, when low concentrations of analytes are to be detected that high background is present with some of these reducible compounds. This high background is due to premature reduction caused by the absorption of light.
There is a need for reducible compounds like those described above which readily release fluorescent dyes for the detection of low concentrations of analytes but which have exceptional stability to light.